Chapter 19, Part 7A - Chuang Tzu

Duke Huan was hunting in a marsh, with Kuan Chung as his carriage driver, when he saw a ghost. The duke grasped Kuan Chung's hand and said, "Father Chung, what do you see?"

"I don't see anything," replied Kuan Chung.

When the duke returned home, he fell into a stupor, grew ill, and for several days did not go out.

A gentleman of Ch'i named Huang-tzu Kao-ao said, "Your Grace, you are doing this injury to yourself! How could a ghost have the power to injure you! If the vital breath that is stored up in a man becomes dispersed and does not return, then he suffers a deficiency. If it ascends and fails to descend again, it causes him to be chronically irritable. If it descends and does not ascend again, it causes him to be chronically forgetful. And if it neither ascends nor descends, but gathers in the middle of the body in the region of the heart, then he becomes ill."
~ Burton Watson translation via Terebess Asia Online ~

Go here to read the introductory post to the chapters of the Book of Chuang Tzu.